The present invention in some embodiments thereof, relates to the field of drip emitters for attachment to an inside surface of a drip irrigation system hose and, in particular, to drip emitters formed of an elastomeric flow control component, and in some embodiments an at least partially surrounding frame component formed of a material that is relatively rigid compared the elastomeric component, and to methods of manufacturing such drip emitters.
Drip emitters for irrigation system hoses provide flow restriction to reduce flow rates to the desired level. Examples of flow restrictors include, but are not limited to, turbulent flow restrictions, laminar flow restrictions, and patterns of meandering fine flow passageways referred to as labyrinths. Labyrinth structures can also be used for pressure reduction.
In some cases, elastomeric materials are employed as part of flow restrictors and pressure reducers. Flow restrictors may be designed to provide variable flow restriction geometry which is responsive to the fluid pressure within the supply hose to at least partially compensate for flow rate variations due to changes in the pressure within the hose. An example of such an arrangement is my U.S. Pat. No. 5,400,973 in which a flat elastomeric diaphragm is deformed by pressure within the hose to sequentially close clearances across the top of a sequence of baffles forming a labyrinth.
The above approach is highly advantageous, providing pressure compensated regulation of the drip outlet flow rate.
As an alternative approach, an elastomeric material may be employed as a bulk material for production of a single piece drip emitter with pressure compensation. Examples of such devices may be found in my U.S. Pat. No. 6,886,761, which employs an elastomeric labyrinth with varying height baffles such that a pressure increase in the hose sequentially closes a bypass channel formed between the baffles and the wall of the hose. A further example is my published Patent Application No. WO 2008/035335 in which an elastomer labyrinth is formed from baffles with an upright upper wall portion and a thickened root portion which forms a sloped transition region between the upper wall portion and the base. In this case, when the fluid pressure within the irrigation hose increases, the sloped transition region becomes progressively flattened to define increased turbulence flow path geometry, thereby regulating the flow rate through the drip emitter.
Additionally, reference is made to my U.S. Pat. No. 5,203,503 which discloses a bi-component drip emitter produced by a bi-component injection molding technique. The bi-component injection molding technique perform two-stage injection with relative movement of the mold parts between stages, resulting in a unitary structure in which an elastomeric element defining a fine laminar flow restriction is implanted within a rigid polymer device. This requires a small quantity of elastomeric material to provide a variable geometry flow restriction while the rest of the drip emitter structure is formed from rigid polymer material.
Additional background art includes international published patent application WO 2006/030419 to Einav, U.S. Pat. No. 5,400,973 to Cohen, U.S. Pat. No. 5,829,685 to Cohen, U.S. Pat. No. 5,183,208 to Cohen, Israeli patent no. 139535 to Cohen, U.S. Pat. No. 5,636,797 to Cohen, and U.S. published patent application 2003/0057301 to Cohen.